Pneumatic tire with carcass cord strip wound in specified pattern

ABSTRACT

A pneumatic tire comprising a belt structure and a torus shaped carcass having a first inner radius and an outer radius, wherein the carcass is comprised of three or more layers of ply, wherein each layer of ply is formed from a rubberized strip of one or more cords, the strips being wound in an geodesic pattern having the cord extend across the carcass from a first shoulder to a second shoulder in a path that has at least one point tangent to the first inner radius located in the bead area of the tire.

CROSS REFERENCE TO OTHER APPLICATIONS

This application claims the benefit of and incorporates by referenceU.S. Provisional Application No. 61/289,754 filed Dec. 23, 2009.

FIELD OF THE INVENTION

This invention relates to pneumatic tires having a carcass and a beltreinforcing structure, more particularly to high speed heavy load tiressuch as those used on aircraft.

BACKGROUND OF THE INVENTION

Pneumatic tires for high speed applications experience a high degree offlexure in the crown area of the tire as the tire enters and leaves thecontact patch. This problem is particularly exacerbated on aircrafttires wherein the tires can reach speed of over 200 mph at takeoff andlanding.

When a tire spins at very high speeds, the crown area tends to grow indimension due to the high angular accelerations and velocity, tending topull the tread area radially outwardly. Counteracting these forces isthe load of the vehicle which is only supported in the small area of thetire known as the contact patch.

Current tire design drivers are an aircraft tire capable of high speed,high load and with reduced weight. It is known in the prior art to usezigzag belt layers in aircraft tires, such as disclosed in the WatanabeU.S. Pat. No. 5,427,167. Zigzag belt layers have the advantage ofeliminating cut belt edges at the outer lateral edge of the beltpackage. The inherent flexibility of the zigzag belt layers also helpimprove cornering forces. However, a tire designed with zigzag beltlayers cannot carry as heavy a load as required by current commercialaircraft design requirements. Further, there is generally a tradeoffbetween load capacity and weight. Thus an improved aircraft tire isneeded, which is capable of meeting high speed, high load and withreduced weight.

DEFINITIONS

“Aspect Ratio” means the ratio of a tire's section height to its sectionwidth.

“Axial” and “axially” means the lines or directions that are parallel tothe axis of rotation of the tire.

“Bead” or “Bead Core” means generally that part of the tire comprisingan annular tensile member, the radially inner beads are associated withholding the tire to the rim being wrapped by ply cords and shaped, withor without other reinforcement elements such as flippers, chippers,apexes or fillers, toe guards and chafers.

“Belt Structure” or “Reinforcing Belts” means at least two annularlayers or plies of parallel cords, woven or unwoven, underlying thetread, unanchored to the bead, and having both left and right cordangles in the range from 17° to 27° with respect to the equatorial planeof the tire.

“Bias Ply Tire” means that the reinforcing cords in the carcass plyextend diagonally across the tire from bead-to-bead at about 25-65°angle with respect to the equatorial plane of the tire, the ply cordsrunning at opposite angles in alternate layers

“Breakers” or “Tire Breakers” means the same as belt or belt structureor reinforcement belts.

“Carcass” means a layer of tire ply material and other tire components.Additional components may be added to the carcass prior to its beingvulcanized to create the molded tire.

“Circumferential” means lines or directions extending along theperimeter of the surface of the annular tread perpendicular to the axialdirection; it can also refer to the direction of the sets of adjacentcircular curves whose radii define the axial curvature of the tread asviewed in cross section.

“Cord” means one of the reinforcement strands, including fibers, whichare used to reinforce the plies.

“Inner Liner” means the layer or layers of elastomer or other materialthat form the inside surface of a tubeless tire and that contain theinflating fluid within the tire.

“Inserts” means the reinforcement typically used to reinforce thesidewalls of runflat-type tires; it also refers to the elastomericinsert that underlies the tread.

“Ply” means a cord-reinforced layer of elastomer-coated cords.

“Radial” and “radially” mean directions radially toward or away from theaxis of rotation of the tire.

“Sidewall” means a portion of a tire between the tread and the bead.

“Laminate structure” means an unvulcanized structure made of one or morelayers of tire or elastomer components such as the innerliner,sidewalls, and optional ply layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view of a tire carcass having geodesic cords;

FIG. 2 is a is a close up view of the cords of the tire carcass in thecrown area;

FIG. 3 is a close up view of the cords of the tire carcass in the beadarea;

FIG. 4A illustrates the initial cord winding on a tire blank in ageodesic pattern;

FIG. 4B illustrates the cord winding on a tire blank of FIG. 4A aftermultiple passes;

FIG. 5 illustrates various geodesic curves;

FIG. 6 illustrates a front view of a tire carcass having geodesic cordsof the present invention;

FIG. 7 illustrates a side view of the carcass of FIG. 7;

FIGS. 8 and 9 illustrate a close up perspective view of the bead area ofthe carcass of FIG. 7;

FIGS. 10-11 illustrate a first embodiment of an apparatus for laying plyon a tire blank;

FIG. 12 illustrates a second embodiment of an apparatus for laying plyon a tire blank; and

FIG. 13 illustrates a cross-sectional view of an aircraft tire.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 13 illustrates a cross-sectional view of an aircraft tire 300 ofthe present invention. As shown, the aircraft tire comprises a pair ofopposed bead areas 312, each containing one or more column beads 320embedded therein. The invention is not limited to same, and a personskilled in the art may appreciate that other bead cores may also beutilized. The aircraft tire 300 further comprises sidewall portions 316which extend substantially outward from each of the bead portions 312 inthe radial direction of the tire. A tread portion 320 extends betweenthe radially outer ends of the sidewall portions 316. Furthermore, thetire 300 is reinforced with a carcass 340 toroidally extending from onebead portion 312 to the other bead portion 312. A belt package 330 isarranged between the carcass 340 and the tread. The belt package may beconventional as known to those skilled in the art or may comprise ageodesic belt. The carcass 340 and geodesic belt package is described ingreater detail, below.

The carcass ply may comprise any suitable cord, typically nylon such asnylon-6, 6. The cord may also comprise aramid or an aramid and nyloncord structure, for example, a hybrid cord, a high energy cord or amerged cord. Examples of suitable cords are described in U.S. Pat. No.4,893,665, U.S. Pat. No. 4,155,394 or U.S. Pat. No. 6,799,618, all ofwhich are incorporated by reference.

Carcass Construction

FIGS. 1-3 illustrate the tire carcass 340 of the present inventionwherein the cords are arranged in geodesic lines. As shown in FIG. 2,the crown portion 341 of an exemplary tire has spaced apart plies withthe angle of about 48 degrees (which varies depending upon the overalltire size). As shown in FIG. 3, the bead area 342 of the tire hasclosely spaced cords with the cords tangent to the bead. Thus the plyangle continuously changes from the bead core to the crown. A geodesicpath on any surface is the shortest distance between two points or theleast curvature. On a curved surface such as a torus, a geodesic path isa straight line. A true geodesic ply pattern follows the mathematicalequation exactly:ρ cos α=ρ₀ cos α₀

wherein ρ is the radial distance from the axis of rotation of the coreto the cord at a given location;

α is the angle of the ply cord at a given location with respect to themid-circumferential plane;

ρ₀ is the radial distance from the axis of rotation of the core to thecrown at the circumferential plane, and α₀ is the angle of the ply cordwith respect to the tread centerline or midcircumferential plane.

FIG. 5 illustrates several different ply path curves of a tire havinggeodesic cords. One well known embodiment of a geodesic tire is theradial tire and is shown as curve 4, wherein the cords have an angle αof 90 degrees with respect to the circumferential plane. Curves 1, 2 and3 of FIG. 5 also illustrate other geodesic cord configurations. Curve 1is a special case of a geodesic cord pattern wherein the cord is tangentto the bead circle, and is referred to herein as an orbital ply. FIGS.4A-4B illustrate a carcass 340 having an orbital ply configuration andin various stages of completion. For curve 1 of FIG. 5, the followingequation applies:At ρ=ρbead, the angle α is zero because the cords are tangent to thebead.α=cos⁻¹(ρbead/ρ)

FIGS. 6-9 illustrate a first embodiment of a green tire carcass of thepresent invention. The cords of the carcass are arranged in a geodesicorbital pattern wherein the cords are tangent to the bead radius of thetire. The close proximity of the cords results in a very large buildupof cord material in the bead area. In order to overcome this inherentdisadvantage, the inventors modified the ply layup as described in moredetail, below.

Apparatus

In a first embodiment of the invention, the tire 300 having a geodesiccarcass is formed on a torus shaped core or tire blank 52. The core hasan outer core surface which may be in the shape of a cylinder such as atire building drum, a buffed carcass for a tire to be retreaded, and ispreferably torus shaped to closely match the interior shape of the tire.The core is rotatably mounted about its axis of rotation and is shown inFIGS. 10 and 11. The core may be collapsible or formed in sections forease of removal from the tire. The core may also contain internalheaters to partially vulcanize the inner liner on the core. The core mayalso be disposable.

Next, an inner liner 305 is applied to the core. The inner liner may beapplied by a gear pump extruder using strips of rubber or in sheet formor by conventional methods known to those skilled in the art. A columnbead 320 of 4 or more wires is applied in the bead area over the innerliner. A first layer of ply is applied over the column bead 320 and theinner liner in a geodesic or orbital configuration as described in moredetail, below. A second column bead 320 is then applied over the firstlayer of ply, and a second layer of ply is applied. A third column bead320 is then applied, and then a third layer of ply is applied in ageodesic or orbital configuration. Each geodesic layer of ply is about300-400 revolutions, and has a thickness equivalent to about 1.5-2.5layers of standard ply. The three layers of geoply in total have anequivalent thickness of about 8 layers of standard ply.

Each layer of ply is formed by winding a strip of rubber coated cords 2in a geodesic or orbital pattern. The cords are applied directly ontothe core over the inner liner as the core is rotated. With reference toFIGS. 10-11, a perspective view of an apparatus 100 in accordance withthe present invention is illustrated. As shown the apparatus 100 has aguide means which has a robotic computer controlled system 110 forplacing the cord 2 onto the toroidal surface of core 52. The roboticcomputer controlled system 110 has a computer 120 and preprogrammedsoftware which dictates the ply path to be used for a particular tiresize. Each movement of the system 110 can be articulated with veryprecise movements.

The robot 150 which is mounted on a pedestal 151 has a robotic arm 152which can be moved in preferably six axes. The manipulating arm 152 hasa ply mechanism 70 attached as shown. The robotic arm 152 feeds the plycord 2 in predetermined paths 10. The computer control systemcoordinates the rotation of the toroidal core 52 and the movement of theply mechanism 70.

The movement of the ply mechanism 70 permits convex curvatures to becoupled to concave curvatures near the bead areas thus mimicking the asmolded shape of the tire.

With reference to FIG. 11, a cross-sectional view of the toroidal core52 is shown. As illustrated, the radially inner portions 54 on each side56 of the toroidal mandrel 52 have a concave curvature that extendsradially outward toward the crown area 55 of the toroidal core 52. Asthe concave cross section extends radially outward toward the uppersidewall portion 57, the curvature transitions to a convex curvature inwhat is otherwise known as the crown area 55 of the toroidal core 52.This cross section very closely duplicates the molded cross section of atire.

To advance the cords 2 on a specified geodesic path 10, the mechanism 70may contain one or more rollers. Two pairs of rollers 40, 42 are shownwith the second pair 42 placed 90° relative to the first pair 40 and ina physical space of about one inch above the first pair 40 and forms acenter opening 30 between the two pairs of rollers which enables thecord path 10 to be maintained in this center. As illustrated, the cords2 are held in place by a combination of embedding the cord into theelastomeric compound previously placed onto the toroidal surface and thesurface tackiness of the uncured compound. Once the cords 2 are properlyapplied around the entire circumference of the toroidal surface, asubsequent lamination of elastomeric topcoat compound (not shown) can beused to complete the construction of the ply 20.

A second embodiment of an apparatus suitable for applying ply in ageodesic pattern onto a core is shown in FIG. 12. The apparatus includesa ply applier head 200 which is rotatably mounted about a Y axis. Theply applier head 200 can rotate about the Y axis+/−100 degrees. Therotation of the ply applier head 200 is necessary to apply the cord inthe shoulder and bead area. The ply applier head 200 can thus rotateabout rotatable core 52 on each side in order to place the ply in thesidewall and bead area. The ply applier head 200 is mounted to a supportframe assembly which can translate in the X, Y and Z axis. The plyapplier head has an outlet 202 for applying one or more cords 2. Thecords may be in a strip form and comprise one or more rubber coatedcords. Located adjacent the ply applier head 200 is a roller 210 whichis pivotally mounted about an X axis so that the roller can freelyswivel to follow the cord trajectory. The ply applier head and stitchermechanism are precisely controlled by a computer controller to ensureaccuracy on placement of the ply. The tire core is rotated as the cordis applied. The tire core is rotated discontinuously in order to timethe motion of the head with the core. The ply applier head and stitcherapparatus is specially adapted to apply cord to the sidewalls of thetire core and down to and including the bead area.

Geodesic Ply Configuration

The strip of rubber coated cords are applied to the core in a patternfollowing the mathematical equation ρ cos α=constant. FIG. 5 illustratesply curves 1, 2, and 3 having geodesic ply paths. Curves 2 and 3illustrate an angle β, which is the angle the ply makes with itself atany point. For the invention, the angle β is selected to be in the rangestrictly greater than 90 degrees to about 180 degrees. Preferably, thegeodesic path (or orbital path) of the invention is ply curve 2 with βabout equal to 180 degrees. For ply curve 2, if a point on the curve isselected such as point A, the angle of ply approaching point A will beequal to about 180 degrees. Likewise, the angle of the ply going awayfrom point A will also be about 180 degrees. Thus for any point on curve2, the angle of ply approaching the point and leaving the point will beabout 180 degrees, preferably substantially 180 degrees.

As shown in FIG. 5, the angle α₀ is selected so that the cord is tangentto the bead. Starting at a point A, the cord is tangent to the bead.Curve 1 of FIG. 5 illustrates the cord path from point A to the centercrown point B, which is an inflection point. The cord continues to theother side of the tire wherein the cord is tangent at point C. Theprocess is repeated until there is sufficient coverage of the core.Depending on the cord size and type selection, the cords are wound for300 to 450 revolutions to form the carcass. Since the cords are tangentto the bead at multiple locations, the build up of the cords in the beadarea form a bead.

As described above, the ply cords are applied to the core in a patternfollowing the mathematical equation ρ cos α=constant. Using a threedimensional grid of data points of the core, a calculation of all of thediscrete cord data points satisfying the mathematical equation ρ cosα=constant may be determined. The three dimensional data set of the coreis preferably X, Y, Ψ coordinates, as shown in FIG. 5. A starting pointfor the calculation is then selected. The starting point is preferablypoint A of FIG. 5, which is the point of tangency of the cord at thebead location. An ending point is then selected, and is preferably pointC of FIG. 5. Point C represents the point of tangency on the oppositeside of the tire compared to point A. Next the change in ψ is calculatedfrom point A to point C. The desired cord path from the starting point Ato ending point C is then determined from the three dimensional data setusing a method to determine the minimum distance from point A to pointC. Preferably, dynamic programming control methodology is used whereinthe three dimensional minimum distance is calculated from point A topoint C. A computer algorithm may be used which calculates each distancefor all possible paths of the three dimensional data set from point A topoint C, and then selects the path of minimal distance. The path ofminimum distance from point A to point C represents the geodesic path.The discrete data points are stored into an array and used by thecomputer control system to define the cord path. The process is themrepeated from point C to the next point of tangency and repeated untilsufficient coverage of the carcass occurs.

Geodesic Ply with Indexing

In a variation of the invention, all of the above is the same except forthe following. The strip is applied starting at a first location in afirst continuous strip conforming exactly to ρ cos α=constant for Nrevolutions. N is an integer between 5 and 20, preferably 8 and 12, andmore preferable about 9. After N revolutions, the starting point of thestrip for the second continuous strip is moved to a second locationwhich is located adjacent to the first location. The strip is not cutand remains continuous, although the strip could be cut and indexed tothe starting location. The above steps are repeated until there issufficient ply coverage, which is typically 300 or more revolutions. Theinventors have found that this small adjustment helps the ply spacing tobe more uniform.

Radius Variation

In yet another variation of the invention, all of the above is the sameexcept for the following. In order to reduce the buildup at the beadarea, the radius p is varied in the radial direction by +/− delta in thebead area of the tire on intervals of Q revolutions. Delta may rangefrom about 2 mm to about 20 mm, more preferably from about 3 to about 10mm, and most preferably about 4 to about 6 mm. The radius is preferablyvaried in a randomized fashion. Thus for example, if Q is 100, then forevery 100 revolutions, and the radius may be lengthened about 5 mm, andin the second 100 revolutions, the radius may be shortened about 5 mm.

Another way of varying the radius is at every Qth revolution, the radiusis adjusted so that the point of tangency is incrementally shortened bygamma in the radial direction, wherein gamma varies from about 3 mm toabout 10 mm. Q may range from about 80 to about 150, and more preferablyfrom about 90 to about 120 revolutions. Thus for example, Q may be about100 revolutions, and gamma may be about 5 mm. Thus for every 100revolutions, the radius may be shortened by 5 mm in the radialdirection. The variation of the radius may be preferably combined withthe indexing as described above.

Axial Variation

In yet another variation, all of the above is the same as described inany of the above embodiments, except for the following. In order toaccount for the buildup at the bead area, the cord axial dimension isincreased in the bead area. Thus there is a deviation in the geodesicequation at the bead area. In the vicinity of the bead area, wherein ρis <some value, a new X value is calculated to account for the buildupof material in the bead area. A new X value is calculated based upon thecord thickness. The new X value may be determined using a quadraticequation. The ρ and a values remain unchanged.

Dwell Variation

In yet another variation, all of the above is the same as described inany of the above embodiments, except for the following. In order toreduce the buildup at the bead area, a dwell angle ψ is utilized. Thusinstead of there being one point of tangency at the bead, the angle ψ isdwelled a small amount on the order of about 5 degrees or less while theother variables remain unchanged. The dwell variation is useful to fillin gaps of the cord in the bead area.

Geodesic Belt Configuration

The crown area of the carcass having a geodesic ply as described abovemay further optionally include one or more geodesic belt. The geodesicbelt is located in the crown portion of the tire between the shoulders.One or more geodesic belts may be applied over the geodesic carcass inthe crown portion of the tire. The geodesic belt may follow the equationρ cos α=constant. The belt may be applied over the carcass using themanufacturing methods described above.

The one or more geodesic belts may also have the following equation:ρ[cos α]^(n)=constant, wherein  (1)0<n<1  (2)Constant=ρ₀[cos α₀]^(n)  (3)If the carcass of the tire is geodesic, it is preferred that n be in therange of about 0.1 to about 0.3. For an aircraft tire, one or moregeodesic belts may be used, preferably two.

Variations in the present invention are possible in light of thedescription of it provided herein. While certain representativeembodiments and details have been shown for the purpose of illustratingthe subject invention, it will be apparent to those skilled in this artthat various changes and modifications can be made therein withoutdeparting from the scope of the subject invention. It is, therefore, tobe understood that changes can be made in the particular embodimentsdescribed which will be within the full intended scope of the inventionas defined by the following appended claims.

What is claimed is:
 1. A pneumatic tire comprising: a belt structure anda torus shaped carcass having a first inner radius and an outer radius,a first and second sidewall, wherein the carcass is comprised of threeor more layers of ply, wherein at least one layer of ply is formed froma rubberized strip of one or more cords, the strip being wound in ageodesic pattern and having the one or more cords extend across thecarcass from a first shoulder to a second shoulder in a path that has atleast one point tangent to the first inner radius located in a bead areaof the tire, wherein a first column bead is positioned between an innerliner and the first layer of ply, wherein the one or more cords aredefined by the equation ρ [cos α]^(n)=K, where n is a positive realnumber greater than 0.1 and less than 1, and K is a constant.
 2. Thepneumatic tire of claim 1 wherein a starting point of the rubberizedstrip of one or more cords is moved to a different location every Nthrevolution and the winding is continued in a geodesic pattern foranother N revolutions, wherein N is an integer in the range of 5 to 15.3. The pneumatic tire of claim 1 wherein a second column bead ispositioned between the first layer of ply and the second layer of ply.4. The pneumatic tire of claim 1 wherein a third column bead ispositioned between the second layer of ply and the third layer of ply.5. The pneumatic tire of claim 1 wherein an angle β of the strip withrespect to itself is strictly greater than 90 degrees.
 6. The tire ofclaim 1 wherein each layer of the ply is formed from a single continuouscord.
 7. The tire of claim 1 wherein the one or more cords is formedfrom a continuous strip.
 8. The tire of claim 1 wherein an angle β ofthe strip with respect to itself is a constant 180 degrees.
 9. The tireof claim 1 wherein the one or more cords are aramid.
 10. The tire ofclaim 1 wherein the one or more cords are polyester.
 11. The tire ofclaim 1 wherein said tire has one or more belt plies, wherein at leastone of said belt plies has cords being defined by the equation ρ [cosα]^(n)=K, where n is a positive real number between 0.1 and 1, and K isa constant.